Defects such as knots, knotholes and cracks make wooden boards unsuitable or undesirable for many structural purposes. Knots, for example, may loosen and fall out after a period of time, may bleed pitch and may remain apparent after painting of the board. Open passages such as knotholes and cracks are inappropriate in many wooden constructions.
Defects of these kinds can be repaired by cutting an opening though the board at the site of the defect and then filling the opening with hardenable mastic or shaped pieces of wood that are adhered together and to the board by means of adhesive. My prior U.S. Pat. No. 4,894,971, issued Jan. 23, 1990 and entitled "Board Repair for Correcting Defects in Lumber or the Like", discloses a particularly advantageous process of this kind. In the repair process of that prior patent, the bore that is cut through the board at the defect site and which is filled with a plug has a width that changes at a first location within the bore and which undergoes a reversed change at another location in the bore. This interlocks the hardened plug material in place and provides a stronger and more durable repair than can be realized by relying solely on adhesive forces to hold the plug in place. My prior U.S. Pat. No. 4,941,305, issued Jul. 17, 1990 and entitled "Repair of Edge Defects in Boards of Lumber or the Like", discloses a method for repairing edge defects in boards that also interlocks the filler material into the board.
Knots and knotholes occur at locations where a branch extended from the trunk or another branch of the tree and the portions of the board that are adjacent the knot or knothole are formed of bark encasement tissue which differs from the wood of other regions of the board. Encasement tissue may also be present as a lining in cracks that existed prior to cutting of the tree. The bark encasement is harder than the adjacent wood, usually has a different coloration and is less absorbent of liquids such as paint.
I have found that the bark encasement can be a source of several problems in connection with board repairs of the hereinbefore discussed kind. The bark encasement does not accept paint as readily as the adjacent wood and filler plug material and may remain visible as a coloration discontinuity in the painted surface. The bark encasement may also detach from the adjoining wood after a period of time and the loosened encasement and plug filler material may than be ejected from the repair site.
In the repair methods of the above identified prior patents, the openings which receive a plug of filler material are formed by drilling passages into the board or by cutting away edge regions of the board. These techniques can be adapted to the repair of elongated cracks but it would be advantageous if the cutting operations involved in the repair of long cracks could be simplified.
Some milling operations, such as the manufacture of bevel siding for buildings, involve resawing of a sawn board along the length of the board to divide it into two boards of smaller thickness. In some instances, such resawing can cut through a repair plug of the above described kind in a manner which causes it to cease to be interlocked into the board. Thus it has heretofore been necessary to defer the repairs until after the resawing. This makes it necessary to perform two repairs to correct what was a single defect prior to the resawing operation. Filler plugs formed after the resawing also may not exhibit the same surface texture or appearance that is found on the contiguous surface of the wood as a result of resawing.
The present invention is directed to overcoming one or more of the problems discussed above.